BIO 352 Lecture Notes - Lecture 6: Mendelian Inheritance, Zygosity, Epistasis

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20 Jun 2018

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Differ from Mendelian genetics due to:

oLinkage

oSex linkage

oEpistasis

oAllelic relationships

Ex. Autosomal Recessive trait

oEither I-3 or 1-4 needs to be heterozygous

oRecessive traits typically skip generations

oRecessive autosomal traits appear equally in both sexes

Autosomal recessive traits

oTrait is rare in pedigree

oTrait often skip generations (hidden in heterozygous carries)

oTraits affects males and females easily

Autosomal Dominant traits

oAlmost always appear in each generation

oAffected individuals all have an affected parent.

oAppear equally in both sexes

oBoth affected sexes transmit to offspring of next generation

No skipping of generations

Generally, affected offspring have affected parent (unless a new

mutation)

oWhen one parent is affected, ½ of the offspring are expected to be affected

oUnaffected parents don’t transmit trait

Sex-linked recessive

oLook for criss/cross pattern of inheritance

oFemale is affected, will all male offspring be affected? Yes

oIf female is carrier, half of her male offspring are predicted to be affected

Sex linked dominant

oSee opposite of criss cross

oAll females from the affected male have the trait, but not all males from affected

females have the trait, this means it must be sex linked and dominant.

oAll daughters should be affected if father is affected

Sex-linked genes, females have 2 copies while male only have 1

Problem 26. CH.5

A gene- color

oA - red (D)

oA - yellow ®

B Gene - Shape

oB -oval (D)

oB -long ®

AaBb x aabb

oDihybrid test cross:

oThose that occur most frequently = Parental type

oStarted with cis, converted to trans

oFrequency of recombinant types; 10/100 = 10%

oOutcome: red, long 46 (½ -x/2)

oYellow, oval 44 ( ½ -x/2 )

oRed, oval 5 (x/2)

oYellow, long 5 (x/2)

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Document Summary

Differ from mendelian genetics due to: linkage, sex linkage, epistasis, allelic relationships. Autosomal recessive trait: either i-3 or 1-4 needs to be heterozygous, recessive traits typically skip generations, recessive autosomal traits appear equally in both sexes. Autosomal recessive traits: trait is rare in pedigree, trait often skip generations (hidden in heterozygous carries, traits affects males and females easily. Autosomal dominant traits: almost always appear in each generation, affected individuals all have an affected parent, appear equally in both sexes, both affected sexes transmit to offspring of next generation. Generally, affected offspring have affected parent (unless a new mutation: when one parent is affected, of the offspring are expected to be affected, unaffected parents don"t transmit trait. If female is carrier, half of her male offspring are predicted to be affected. Sex-linked genes, females have 2 copies while male only have 1. A gene- color: a - red (d, a - yellow .

Related Questions

___1. Nationally, the most common cause of Down Syndrome is
a. nondisjunction of Chromosome 21 during meiosis
b. translocation of Chromosome 21 onto another chromosome
c. inversion of a large section of Chromosome 21
d. deletion of the Down Syndrome gene
___2. In humans, sex is determined by
a. The presence or absence of the Y chromosome
b. The ratio of X chromosomes to sets of autosomes
c. The temperature during fetal development
d. Which parent is stronger at the time of conception
___3. A translocation is
a. a chromosomal abnormality in which a piece of one chromosome breaks off and attaches to a different chromosome
b. an abnormality in which the chromosomes are translocated out of the nucleus
c. a condition in which the chromosome has broken in two places and come back together with the middle segment backward
d. an abnormality in which there is an extra copy of one chromosome
___ 4. In snapdragons, a red-flowered plant crossed with a white-flowered plant produces all pink-flowered offspring. But crossing two pink-flowered plants produces red, pink, and white in a 1:2:1 ratio. This is a good example of
a. Incomplete dominance
b. Dominance of the red allele over the white allele
c. Lethal effects of the pink allele
d. Sex-linkage of the flower-color alleles
___ 5. If a person with type AB blood marries a person with Type O blood, what blood types are possible in their children? (Assume this trait is a single-gene trait, not complicated by interaction with other genes).
a. A, B, AB, or O
b. A or B only
c. AB or O only
d. AB only 2
___6. In what phase of meiosis are haploid nuclei first formed? a. Anaphase I b. Metaphase II c. Telophase II d. Metaphase I e. Telophase I
___7. What is the phenotype of a heterozygous tall pea plant? a. tall b. Tt c. TT d. tt e. dominant
___ 8. If genes A and B are far apart on a chromosome, and A and C are close together, which of the following observations is expected?
a. Crossing over will occur more often between A and C than between A and B
b. Crossing over will occur at equal frequencies between A and C, and between A and B
c. Crossing over will occur more often between A and B than between A and C
___9. Sometimes an organismâs genotype for one gene masks the effect of a different gene. This phenomenon is called
a. Dominance
b. Incomplete dominance
c. Co-dominance
d. Epistasis
e. Variable expressivity
___10. The dominant allele of a gene is
a. The one that is expressed most often in a population
b. The one that is expressed most often in any particular cross
c. The one that is expressed in an individual that has two different alleles
d. The one that is most healthy to have, that gives the greatest fitness
___11. In human cells, DNA replication occurs
a. In S phase of interphase
b. In G1 phase of interphase
c. In G2 phase of interphase
d. In prophase of mitosis
e. Whenever the cell needs to read the DNA to make proteins
___ 12. A process in which recipient cells take up genes from DNA molecules floating free in the surrounding medium is called
a. conjugation
b. specialized transduction
c. generalized transduction
d. transformation 3
___ 13. Most calico cats are female. However, a few rare males are observed. What is the genotype of a male calico cat?
a. X BX 0
b. X OY
c. X BY
d. X BYY
e. X BX OY
___ 14. A type of red-green color-blindness is a sex-linked (X-linked) recessive trait in humans. Can a woman have this type of color-blindness?
a. Yes, a woman could be color-blind if her mother and father were both heterozygous.
b. Yes, a woman could be color-blind but only if she has an abnormal number of sex chromosomes.
c. No, women can't show sex-linked traits because they lack a Y chromosome.
d. No, women can't show sex-linked traits because they have two X chromosomes.
e. Yes, a woman could be color-blind if her father was color-blind and her mother was a carrier (heterozygous).

BIO 352 Lecture Notes - Lecture 6: Mendelian Inheritance, Zygosity, Epistasis

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